John Phillips wrote:

I often see texts that imply or state outright that ringing in time-domain
audio waveforms, usually associated with time-domain discontinuities,
is to be avoided. I wonder what is the basis for this.

Ringing on square wave inputs may be a sign of maginal stability.

Graham

On 2008-07-08, Eeyore wrote:
John Phillips wrote:

I often see texts that imply or state outright that ringing in time-domain
audio waveforms, usually associated with time-domain discontinuities,
is to be avoided. I wonder what is the basis for this.

Ringing on square wave inputs may be a sign of maginal stability.

Indeed. For ringing in an "analogue" sense. I was actually thinking
of digital systems and I see now the multiple uses of "ringing" so I
should have clarified.

--
John Phillips

John Phillips wrote:

Eeyore wrote:
John Phillips wrote:

I often see texts that imply or state outright that ringing in time-domain
audio waveforms, usually associated with time-domain discontinuities,
is to be avoided. I wonder what is the basis for this.

Ringing on square wave inputs may be a sign of maginal stability.

Indeed. For ringing in an "analogue" sense. I was actually thinking
of digital systems and I see now the multiple uses of "ringing" so I
should have clarified.

In digital it could be anything, even down to fundamentals of the theDSP filter
structure.

Graham

In article , Eeyore
wrote:


John Phillips wrote:

I often see texts that imply or state outright that ringing in
time-domain audio waveforms, usually associated with time-domain
discontinuities, is to be avoided. I wonder what is the basis for
this.

Ringing on square wave inputs may be a sign of maginal stability.

Key phrase here is "may be". I recall reading in the past more than one
review of a power amp where the writer assumed that 'ringing' on a square
wave was a sign of marginal stability. Whereas in many cases it simply
showed that the amp included a series inductor on its output to ensure safe
and stable operation into naster RF loads. Another example where it was
possible for writers to jump to conclusions based upon limited
understanding.

My impression is that it has been common for digital filtering in domestic
items like CD players to use FIR arrangements. Stability should not be a
problem for these. But may be more of an issue for IIR designs. Indeed, if
I recall correctly, some of the high order delta-sigma modulator (i.e. ADC)
arrangements published by Sony and Philips for DSD/SACD had potential
instability unless used correctly.

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

On 2008-07-08, Jim Lesurf wrote:
In article , Eeyore
wrote:
John Phillips wrote:
I often see texts that imply or state outright that ringing in
time-domain audio waveforms, usually associated with time-domain
discontinuities, is to be avoided. I wonder what is the basis for
this.

Ringing on square wave inputs may be a sign of maginal stability.

Key phrase here is "may be". I recall reading in the past more than one
review of a power amp where the writer assumed that 'ringing' on a square
wave was a sign of marginal stability. Whereas in many cases it simply
showed that the amp included a series inductor on its output to ensure safe
and stable operation into naster RF loads. Another example where it was
possible for writers to jump to conclusions based upon limited
understanding.

My impression is that it has been common for digital filtering in domestic
items like CD players to use FIR arrangements. Stability should not be a
problem for these. But may be more of an issue for IIR designs. Indeed, if
I recall correctly, some of the high order delta-sigma modulator (i.e. ADC)
arrangements published by Sony and Philips for DSD/SACD had potential
instability unless used correctly.

So, in summary it seems that there are some causes of time-domain audio
signal ripples ("ringing" as a description of the observed phenomenon)
that may indicate problems in an audio system. One of those problems
may be "ringing" as a cause of the observed phenomenon, associated with
marginal stability in both an analogue and a a digital sense.

However it also seems clear that the Pavlovian response sometimes seen
in audio contexts to the observation of a "ringing" waveform is probably
not necessarily appropriate.

--
John Phillips

In article , John Phillips
wrote:

So, in summary it seems that there are some causes of time-domain audio
signal ripples ("ringing" as a description of the observed phenomenon)
that may indicate problems in an audio system. One of those problems
may be "ringing" as a cause of the observed phenomenon, associated with
marginal stability in both an analogue and a a digital sense.

I'd say the distinction here is between a symptom - visible ripples or
ringing associated with something like a transient - and assigning a
'cause' of that observed behaviour. The problem is that there are various
possible causes.

However it also seems clear that the Pavlovian response sometimes seen
in audio contexts to the observation of a "ringing" waveform is probably
not necessarily appropriate.

Yes. In practice this is perhaps another example of a common problem in
areas like domestic audio. That a commentator may decide they have spotted
a symptom, and then jumps to a conlcusion about the cause - perhaps being
completely mistaken. Similar to the case of 'Dirty Digital' in another
thread, where someone does a measurement in an inappropriate manner, and/or
misunderstands the results they see. The symptom (FFT analyser display in
that case) is correct - for the given situation - but this symptom then
prompts an incorrect diagnosis of the cause. :-)

Alas, it is one thing to give someone a lot of nice test kit. It is
something else for them to use it correctly, and recognise what the results
do (or do not!) tell them.

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html